The present disclosure relates generally to medical devices for use in patient care. The present disclosure relates more particularly to a medical device for the diagnosis and treatment of ventricular desynchronization in a patient.
Ventricular desynchronization is a heart condition that typically occurs in two forms: (1) spatial desynchronization and (2) temporal desynchronization. Spatial desynchronization and temporal desynchronization may occur independently or in combination with each other.
In spatial desynchronization, a cardiac conduction disorder causes a delay in the contraction of one of the heart ventricles (i.e., the left ventricle or the right ventricle) relative to the contraction of the other ventricle, leading to deterioration in the hemodynamic status of the patient. U.S. Patent Application Publication No. 2005/0027320 A1 (granted as U.S. Pat. No. 7,092,759) discloses a device for the detection of the desynchronization between the two ventricles (i.e., spatial desynchronization). The disclosed device allows for the assessment and application of an appropriate stimulation therapy, including the optimization of the interventricular delay (VVD).
Temporal desynchronization is characterized by a late contraction of all or part of the left ventricle in relation to the closure of the aortic valve. In temporal desynchronization, some segments of the ventricular wall are still in a contracted state during the diastolic phase (i.e., after the ejection of blood into the aorta, during the closing of the aortic valve) and, in extreme cases, after the opening of the mitral valve, (i.e., at the beginning of the phase of passive filling of the left ventricle with blood from the left atrium). Temporal ventricular synchronization may be characterized by the presence of diastolic contraction (i.e., with setback) of some segments of the left ventricle with an antagonistic effect on the hemodynamic activity and a decrease in ejection fraction, considered the reference hemodynamic parameter.
These ventricular desynchronizations can be treated by a Cardiac Resynchronization Therapy (CRT) or Bi-Ventricular Pacing (BVP) technique consisting of implanting a device with electric leads (i.e., electrodes) in the patient to stimulate one or both ventricles at various ventricular locations. The device applies an appropriate interventricular delay (VVD) between the respective moments of stimulation of the right and left ventricles. The VVD may be adjusted to resynchronize the contraction of the ventricles with fine tuning of the patient's hemodynamic status. The VVD can be zero, positive (i.e., the left ventricle being stimulated after the right ventricle) or negative (i.e., the right ventricle being stimulated after the left ventricle).
Various global assessment techniques of hemodynamic function in a patient are known. For example, European Patent Application Publication No. 1108446 A1 (ELA Medical S.A.) evaluates hemodynamic function using an intracardiac bio-impedance measurement. The intracardiac bio-impedance measurement is a parameter indicative of the cardiac output and thus of the ejection fraction. Another example is provided in European Patent Application Publication No. 2092885 A1 (Sorin CRM S.A.S), which extracts information from an endocardial acceleration signal and combines various indicators representative of the patient's hemodynamic status. However, these devices operate a non-specific diagnosis of ventricular desynchronization, without distinction between temporal and spatial desynchronization.
International Publication No. WO 95/27531 A1 discloses a device, provided in particular with one or more velocity or acceleration sensors measuring the displacement of the heart wall in order to determine whether myocardial contractions are occurring. The sensor can be an endocardial acceleration (EA) sensor which produces a signal reflecting, in the form of two peaks, the two heart sounds produced by the closing of the mitral valve and at the opening of the aortic valve. Measuring the height of one or the other peak of the EA signal provides an indication of whether any mechanical activity of the heart is occurring. In the absence of mechanical activity of the heart, the device issues an appropriate bradycardia therapy (e.g., conventional stimulation of the DDD or DDI type). However, in the presence of a mechanical activity, therapy is inhibited so as not to interfere with the spontaneous contractions of the myocardium.
U.S. Pat. No. 7,212,861 and European Patent Application Publication No. 2495013 describe various techniques for search of an optimal stimulation configuration based on the detection of the mechanical activity of the ventricle. However, like the documents, they do not consider the specific diagnosis or treatment of any possible ventricular desynchronization.
Current treatments and devices do not provide a specific method to diagnose the temporal desynchronization of the ventricle, regardless of any consideration relating to possible spatial desynchronization. In particular, current treatments and devices do not distinguish between temporal and spatial desynchronization or apply differentiated therapies according to the type of disorder. While it is generally sufficient to apply biventricular pacing with VVD (e.g., as described in U.S. Patent Application Publication No. 2005/0027320 A1) to address spatial desynchronization, the treatment of temporal desynchronization—which involves only one ventricle—may require a much finer adjustment of various stimulation parameters. The stimulation parameters may include, for example, the atrioventricular delay (AVD) and/or a combination of AVD and VVD. The specific detection of a temporal desynchronization may help to treat, or possibly even cure, a disorder which is untreated or inadequately treated by conventional CRT therapy.